Project Summary Extended X-ray absorption fine structure (EXAFS) is a technique that gives element- specific structural and chemical information about molecules. EXAFS currently requires bright X-ray beams from specialized synchrotron light sources for most samples and so its applications are limited by access to these facilities. This project will involve improved X-ray detectors based on superconducting tunnel junctions (STJs) to achieve the resolution and efficiency needed to make EXAFS measurements of many samples feasible in a laboratory setting without synchrotrons. This goal has two specific aims: 1) development of next-generation STJ detectors with the needed resolution and efficiency; and 2) integration of the detector into a complete instrument for performing EXAFS in the laboratory. To achieve the required detector performance for this task, STAR Cryoelectronics will combine previous success with tantalum-based STJs and another design based on aluminum junctions to make molybdenum-based junctions that are more compatible with available manufacturing methods compared to aluminum. The detector will be coupled with a sample chamber and X-ray source to make a complete, user-friendly EXAFS instrument. Phase I of this project will involve fabrication of the first examples of Mo-STJ detectors to verify their functionality and design parameters, as well as conducting initial soft X-ray EXAFS with existing STJ detectors to test predicted statistics and resolution requirements. This instrument will reduce the need to apply for access to synchrotrons for EXAFS and open up the technique for more general and routine chemical and biological applications.